The present invention relates to a tool for use in fishing electrical wires through a wall and, more particularly, to such a tool that utilizes an electromagnet for selectively attracting magnetic objects such as fish tape.
Electricians and other installers of electrical fixtures and telephones in dwellings, offices and commercial buildings spend a significant amount of time running electrical conduit or wire through walls. The running of wire is necessary to establish the connection between a fixture and a corresponding power source. In some instances, a length of fish tape is first inserted through a hole in a wall and positioned adjacent a different hole some distance away. The wire to be installed is then secured to the one end of the fish tape. Thereafter, the other end of the tape is pulled through the wall so that the wire is drawn through the same.
It is often difficult to insert either the fish tape or electrical wire through one hole in a wall and manipulate the same so that one end of the tape or wire can be positioned adjacent another second hole. In recognition of the aforementioned problem, magnetic fishing tools have been developed that aid in the insertion of the fish tape and/or electrical wire through the wall.
U.S. Pat. No. 3,078,073, for example, discloses an electrical wire finder that includes a conductor holder and a sensor made of magnetizable material. In use, the conductor holder, with a conductor secured thereto, is inserted into a hole in a wall. Thereafter, the sensor is lowered from an area where the connecting cable or wire is located, via a flexible line, to the vicinity of the conductor holder. The conductor holder has a magnet secured thereto. Accordingly, the conductor holder and sensor are attracted to one another. The operator can then raise the flexible line to carry the conductor to the connecting cable in order to establish the required electrical connection.
A problem associated with this prior art device is that the conductor holder has a permanent magnet secured thereto. Accordingly, as it is inserted into the wall it attracts anything that is made of magnetic material. This interferes with the insertion and positioning of the conductor holder. Furthermore, since the line secured to the sensor is flexible, the sensor cannot be pushed upwardly through a wall. More specifically, if the holder and attached conductor are located adjacent a first hole positioned above a second hole, the sensor could not be inserted through the second hole and up toward the first hole because the line has no structural rigidity.
U.S. Pat. No. 3,971,543 discloses a tool for fishing electrical wires through walls that includes a magnetic sensor. One end of the sensor is connected to a length of chain while the other end has a fastener member which is secured to a line or wire. In use, a cylindrical member, which houses a permanent magnet therein, is inserted through a hole in the wall to attract the sensor assembly which is suspended within the wall. Once again, this device is only useful in allowing an operator to position the line or wire from an upper location to a lower location as the chain has no structural rigidity. Additionally, the magnet secured to the cylindrical housing cannot be selectively energized or deenergized.
U.S. Pat. Nos. 4,527,775 and 4,572,561 also disclose devices for installing wire or conduit. However, these devices are relatively complex and unwieldy.